Method and apparatus for handling powdered material



Aug. 22, 1939. 2,170,258

METHOD mp APPARATUS FOR HANDLING POWDERED MATERIAL N. s. BORCH Filed Aug. 26, 1937 TO R 7 d4.

Patented, Aug. 22, 1939 v UNITED STATES,

PATENT OFFICE METHOD AND APPARATUS FOR HANDLING POWDERED MATERIAL Niels Sofus Burch, Copenhagen, Denmark, as-

signor to F. L. Smidth & Company, New York, N. Y., a corporation of New Jersey Application August 28, 1937, Serial No. 160.954

In Great Britain August 27, 1936 2'Claims. This invention relates to apparatus for handling powdered material and is concerned more particularly with a novel method of storing and discharging powdered material expeditiously and s a new apparatus by which that method can be practiced. The new apparatus is simple in con-,

struction and reliable in operation and is adapted for manufacture at low cost.

For the purpose of illustration the principles it In the handling of cement, it is common to store the cement in powdered form in a container or silo from which the cement may be discharged asdesired from the bottom or sides of the silo, usually either by gravity or pneumatically. The dis- 20 charge of the cement will often take place at an even rate until the silo is partly emptied, whereupon the discharge will suddenly cease due to the formation of bridges of thepowdered cement across the discharge opening, these bridges being 25 formed by cohesion between the particles of cement. When the material is discharged through an opening in thetbottom of the silo, it frequently forms firmly packed, funnel-shaped walls flaring upwardly from the discharge opening, whereby an continuation of the discharge is prevented. Also, particles of the cement may adhere to the inner surface of the silo walls and other particles cohere to these particles, this action being cumulative until a body of the cement is fixed to the sun walls which is of sufiicient size to materially impede the discharge of the cement.

The present invention is directed to the provision of a novel method and apparatus for maintaining powdered cement in a fluid-like con- 40 dition and for discharging the cement rapidly and continuously as desired.

In accordance with the method of the present invention, the powdered cement is stored in a container, such as a silo, and air entrained in the material is alternately compressed and expanded at a relatively rapid rate, whereby the entrained air isiorced back and forth through the particles with a vibratory motion. The entrained .air is thus stirred through the particles of cement. so that the cement is maintained in a fluidlike condition. Preferably, the rate at which the entrained air is alternately compressed and expanded is such that the particles of cement cannot readily follow the movement of the air our- 55 rents incident to the expansion and compression of the entrained air, and by so regulating the frequency of the vibratory movement of themtrained air the particles of cement remain substantially stationary during the stirring action. In the preferred method, the alternate compres- 6 sion and expansion of the entrained air is. effected by vibrating at least part of the inner surface of the silo walls adjacent the discharge opening. whereby the material near thewalls will acquire the properties of a fluid and readily lend itself 10 to discharge. The alternate compression and expansion of the entrained air may be effected continuously as long as material remains in the silo or, alternatively, the compression and expansion of the air may be effected only when some or all of the material is to be discharged. If desired, the entrained air in the material at the mouth of the discharge opening in the silo may be forced back and forth through the material .so as to prevent cohesion of the particles at this region.

An apparatus constructed in accordance with I the principles of my invention comprises a silo or other container having means therein for foreing the entrained air in the material back and forth through at least part ofthe material ad- 26 jacent the walls of the silo at a frequency in excess of that at which the particles of cement can readily follow the aircurrenta The entrained air may be conveniently forced or stirred through the cement by one or more diaphragms disposed 3 in the silo and adapted to be vibrated by suitable q means. Preferably, a vibrating member is also disposed at the mouth of the discharge opening in the silo, the latter member serving to maintain the material near the fluid-like condition.

For a better understanding of the invention reference may be had to the accompanying drawing in which Fig. 1 is a vertical section through one form' of 40 the new apparatus;

Fig. 2 is a section on the line 2-2 of Fig. 1;

Fig. 3 is a detailed view in section of part of the silo wall showing a diaphragm for alternately compressing and expanding the entrained air in the silo; and

Fig. 4 is a detaiied view partly in section showing a modified form of the diaphragm and the actuating means therefor. I

Referring to the drawing, the numeral in designates a silo having a circular concrete side wall ll and-"a concrete wall i2 tapering downwardly therefrom to a discharge opening it. The inner surface of the sloping wall ll of the silo is provided with a plurality of recesses l4 discharge opening in a 35 opening through which a pipe I 6 extends, the

pipe being provided at its innerend with a sealing member H. An annular frame l8 of rubber or the like is .disposed in each of the recesses 84 over the plate 1'5 and has'a diaphragm l9 mounted on the inner end thereof, preferably flush with the inner surface of the silo wall It.

The annular frame i8and diaphragm l3 are held in position by means of bolts 26 extending inwardly through the plate, frame and diaphragm, each of the bolts at having a nut 2i threaded on the inner end thereof. The diaphragm i9 may be of any suitable material, such as metal, and the plate IE5 and diaphragm are held tightly against the annular frame it so that the recess It is air tight.

Each of the pipes l6 extends outwardly from its corresponding recess it through the concrete wall l2 and has a suitable valve 23 therein. The pipes I3 extending from the recesses near the top or the sloping wall i2 lead to a! common pipe 24 which, in turn, leads to one end of a cylinder 25. Similarly, the pipes l3 extending outwardly from the recesses l4 near the bottom of the sloping wall 52 are connected to acommon pipe 26 which leads to the cylinder through part of pipe 24. Another pipe 21 leads from the common pipe 24 to an expansible and contractible chamber 28 disposed in the discharge opening l3 in the silo. The chamber 28 may be of any desired construction, but is illustrated as a rectangular member having flexible side walls 28'. Valves 29 and 30 arelocated in the pipes 26 and 2'5, respectively, whereby the respective chambers to which these pipes lead may be shut off from the common pipe line 24 without aifecting the other chambers. Also, a valve 3| is located in the pipe 24 near the chambers 84 so that the latter chambers may be shut oil from the cylinder 25 without afiecting the chambers supplied by pipes 26 and 21.

A piston 33 is disposed in the cylinder 25 and is adapted to be oscillated therein ata rapid rate by an arm 34 pivoted to the piston at 35. The lower end of the arm'34 is enlarged and is provided with an opening through which an eccentric 35 extends. The eccentric 35 is mounted on a drive shaft 36 which is driven by any suitable means (not shown). The closed system including the. chambers i4, expansible and contractible chamber 28, cylinder 25 and the connecting pipes are filled with a suitable fluid, such as air, water or oil. Accordingly when the piston 33 is oscillated in cylinder 25 upon rotation of drive shaft 36, the pressure of the fluid in the closed system will be alternately increased and decreased at a rate depending upon the speed of rotation of drive shaft 36, and this will cause the diaphragm l9 and flexible walls 28' to vibrate at a corresponding frequency.

' Upon vibration of the diaphragms IS, the diaphragms will at one moment press the material adjacent thereto against the inner mass of material and at the next moment will move in the opposite direction so'as to create a reduction in the pressure of the entrained air in the cement adjacent these members. ,This reduction in pressure, however, will be released almost immediately by entrained air which is sucked from the contents of the silo near the middle thereof. The

dlaphragms 19 will then move-back in the opposite direction andv thereby force the air through the adjacent material toward the interior of the .silo. This action will be repeated continuously so-that the powdered cement will be mixed and stirred with air, whereby the material near the walls oi the silo will acquire the properties of a fluid and will flow or slide in the desired manner when the silo content is to be discharged.- The walls 24' of the expanslble and contractible chamber 23 will act in a similar manner to'maintain the cement near the discharge opening l3 in a fluid-like condition. It will be understood that. the frequency at which the members l3 and 23' are vibrated shouldbe sufficiently high so that the particles of cement through which the airis stirred cannot readily follow the air cur-,

illustrated in Fig. 4 of the drawing. As there shown, each diaphragm |3'- is provided on its inner face with an armature 33 of magnetic material. An electromagnet 33 is mounted on the silo wall I! adjacent the armature 33 and is adapted to be energized through wiring 40 by a generator 4|. The generator'4l is driven by a motor 42 and is adapted to deliver a. pulsating current to the electromagnets so that the attractive action of the' electromagnet on the armature 38 will alternately increase and decrease rapidly. The diaphragm 13' will thus be vibrated to provide the stirring action in the hi6 previously referred to. Preferably, the position of the electromagnet 33 relative to the diaphragm is the attractive force exerted by the magnet on the diaphragm may be varied.

It will be observed that the apparatus of the present invention is of a simple construction which may be manufactured at a relatively low cost and is adapted to maintain the powdered material in storage in a fluid-like condition. The diaphragms and the mechanism for vibrating them may be readily installed in a container of any desired form and operate independently 01' the container. It will be understood that while the diaphragms I! have been described and illustrated as being mounted in the walls 01 the container or silo, they may be installed ii desired in the container in spaced relation to the walls thereof.

I claim:

1. Apparatus for handling powdered material comprising a container having a discharge opening, anexpansible and contractible chamber disposed in the mouth of the opening and spaced on all sides from the surrounding walls of said opening, a fluid-containingsystem of which said chamber forms a part, a pressure fluid in said system, and means which also forms .part 01 said fluid-containing system for alternately increas-' ing and decreasing the pressure on said fluid to vibrate at least one ofthe' walls of said chamber,

ing a wall sloping downwardly to a discharge opening, the combination of a diaphragm disposed in the container adjacent said sloping wall,

taming system. for alternately increasing and decreasing the pressure on said fluid to vibrate at least one of the walls of said chamber, said fluid being completely and constantly confined in said system;

. NIELS SOFUS BORCH. 

